Document G56ZO82QLGRE7nEGpxXzwe1GY

Certairileed Date April 16, 1980 Subject Project 345 A/C Curing Investigation: Double Autoclave at Plant 258 To F. Niedergang From B. Jo /n/ Location and mail code BB 2126 Location and mail code cc: J. McGialey H. Benhardt Enclosed is an R&D report on the subject matter. It has proved that the double autoclaving improves the crush strength. The degree of crush strength improvement was known to be parallel with hydro strength improvement in the range of our interest. However, it is not certain that the degree of improvement observed in this investigation is really critical for turning a batch of product from failure to passing the specification. Improvement by the double autoclave seems to be the result of the combined effect of wetting with water prior to double autoclave and the autoclave reaction. This raises a question as to whether the moisture content of the pipe prior to the 1st autoclave was sufficient. If not, water treatment prior to the 1st autoclave could eliminate the double autoclave. BHJ/pha RECEIVED.'- 1 7 1980 01-25-0005 CT-1703 CTD001314 CertainTeed Date April 7, 1980 Subject PROJECT 345 A/C CURING INVESTIGATION To Location and mail code Dr. B. Jo BB #2126 Fram 7. Ma&y -tv*. Location and mail code J.A. Malone/db BB #2126 cc: Mr. F. Niedergang Mr. J.P. McGinley Mr. H. Benhardt - BB 2126 - VF P6PG #2B - Ambler #258 INVESTIGATORS: John A. Malone John P. Ungerman John W. Hoover John R. Magargal OBJECTIVES: To determine the increase in crushing strength resulting from "double autoclaving" at plant 258, using both the plant and the experimental shop autoclaves. CONCLUSIONS: 1) . "Double Autoclaving" produced about a 4.3 percent increase in average modulus of rupture in crush. 2) . The' samples autoclaved at the experimental shop were about 2.6 percent higher in crush modulus than those autoclaved at plant 258, making the results approx imately equivalent. 3) . A very good correlation exists between crush modulus and density. 4) . Differential thermal analysis for tobermorite and unreacted silica tends to confirm an increase in strength with "double autoclaving". 01-25-0005 CT-1703 CTD001315 PROJECT 345 -A/C CURING INVESTIGATION- -Page 2- PLANS AND RECOMMENDATIONS: 1) . Evaluation of "double autoclaving" in the laboratory under various precure, autoclaving, and wetting conditions. 2) . Use of cements and silicas from the various asbestos-cement pipe plants in these laboratory studies. 3) . Recommendations to the asbestos-cement pipe plants and quality control based on present and future test data. KEY WORDS: Asbestos-cement pipe, autoclaving, crushing strength, curing, manufacturing, tobermorite. CTD001316 CURING INVESTIGATION ASBESTOS-CENENT (DOUBLE AUTOCLAVING AT PLANT 258) PROJECT 345 JOHN A. MALONE JOHN P. UNGERMAN JOHN W. HOOVER JOHN R. MAGARGAL APRIL 11, 1980 CTD001317 -Page 4- CONTENTS I. INTRODUCTION II. EXPERIMENTALMETHODS III. RESULTS IV. DISCUSSION V. RECOMMENDATIONS PAGE 5 5 8 11 12 CTD001318 -Page 5- INTRODUCTION: 1). Plant 258 has frequently found it necessary to "double autoclave" 6-inch and 8-inch pressure pipe in order to meet the specified strength require ments. This "double autoclaving" cycle is as follows: (a) The pipe is autoclaved for 14 hours with saturated steam at 145 to 150 psig (usually within 2 to 8 hours after removal from the last precure tunnel). There is no rewetting of the pipe at this stage. (b) The pipe is removed from the autoclave and cooled (this time varies up to several days depending on autoclave availability for the sec ond cycle). (c) The pipe is wet with water using a hose, and is then autoclaved for an additional four hours with steam at 145 to 150 psig. (d) In all cases, the autoclave is charged and blown down over about a 45 to 60 minute period. The present study was designed to determine the increase in crushing strength for 8"-150 pipe resulting from "double autoclaving" at plant 258, and from "double autoclaving" under similar conditions at the experimental shop in Blue Bell. The purpose of the Blue Bell study was to evaluate strength increase under carefully controlled conditions for comparison with plant practice: EXPERIMENTAL METHODS: 1) . Two 8"-150 pipe were selected and marked before entering the first precure tunnel so as to be certain that they had identical treatment at rollup, breaking, and calendering. 2) . At the end of the second precure tunnel, these two pipes were removed, cut and the pieces identified as indicated in Figure 1. The first six inches were discarded for both pipe. CTD001319 -Page 6- 3) . The "L" samples were sent to Blue Bell for autoclaving in the Experimental Shop; the "P" samples were autoclaved at plant 258 together with the regular production from which they were selected. 4) . The following autoclaving cycles were followed at the two locations: (a) Plant 258 The procedure listed in (a) thru (d) under INTRODUCTION was followed at plant 258. All the "P" samples were autoclaved for 14 hours; only the P^, Pg and P6 samples were autoclaved for the additional four hour period. (The time after removal from the second tunnel until the start of pressure build up for the first autoclaving cycle was 6 hours; the time after blow down until the start of pressure build up for the second autoclaving cycle was three days). It should be noted that the P^ and Pg sections from Pipe I, and the P(2 and Pg sections from Pipe 2 were used for control purposes. (b) Experimental Shop The same procedure was followed relative to scheduling and autoclaving conditions in the Experimental Shop as at plant 258. All the "L" samples were autoclaved for 14 hours; only the L4, L5 and Lg samples were auto claved for the additional four hour period. 5) . After autoclaving was complete, one-inch rings were cut from each of the 13-inch samples, as indicated in Figure I, for density determinations. All samples were held at room conditions in the Experimental Shop for approximately five days prior to test. CTD001320 -Page 7- 6). The following tests were then run in accordance with the procedures indicated (a) Crushing Strength Standard Wood Block Crush Test according to ASTM Method C500-77, entitled Standard Methods of Testing Asbestos-Cement Pipe. The modulus of rupture in crush was calculated as follows: MR _ (0.955)(ID + tR)(P) (12)(tB)^ WHERE MR = Modulus of Rupture - lbs./sq.in. ID = Inside Diameter-inches = Thickness at break-inches P = Crush load-pounds/foot 12 = inches/foot 0.955 = constant (b) Density CertainTeed Technical Specification TM-5, entitled Water Displacement Density Test Method for A/C Products. CTD001321 RESULTS: Sample Pi P2 p3 Ll l2 L3 p4 p5 p6 l4 L5 l6 pA PB pc PD TABLE I - CRUSHING STRENGTH Crush Load lbs./ft. 5329 7004 6560 6854 6848 6414 7368 7133 7065 6522 7770 7460 6384 6360 6747 6596 Thickness at break tR-inches 0.780 0.833 0.828 0.825 0.837 0.818 0.833 0.828 0.818 0.810 0.830 0.828 0.800 0.830 0.823 0.833 ID + tB inches 8.683 8.740 8.752 8.729 8.754 8.720 8.747 8.800 8.773 8.694 8.792 8.784 8.698 8.744 8.717 8.770 -Page 8- Modulus of Rupture lb./sq.inches 6053 7021 6665 6996 6810 6652 7392 7286 7372 6878 7892 7607 6905 6424 6910 6635 CTD001322 SAMPLE D1 D2 6 D3 D4 D5 TABLE II - DENSITY PIPE SECTION P1 P2 P6 L3 L4 L5 AVERAGE DENSITY lb./cu.: 0.0626 0.0633 0.0646 0.0627 0.0635 0.0644 0.0635 -Page 9- CTD001323 -Page 10- TABLE III - DIFFERENTIAL THERMAL ANALYSIS (DTA) Sample Ll ?2 Average L5 P4 Average Modulus of rupture lbs./sqin. 6996 7021 7009 7892 7392 7642 Tobermorite Exotherm (area-in. X 100) Unreacted S1O2 Endotherm (area-in^ X 100) 310.8 320.0 315.4 7.0 7.8 7.4 336.0 313.0 324.5 7.5 6.5 7.0 NOTE: L^ and P2 samples were "single autoclaved". Lg and P^ samples were "double autoclaved". DTA diagrams obtained with Delta Therm Model D2000 apparatus at a hearing rate of 10C per minute, using left oven with #1 sample holder. All results are an average of four sample tests. CTD001324 2"/ ^ " /c- wpi s z y'/^/v /a/ p/ps____________ ^//V^ 7~Z737~ y?i~r ^ 7~-S~_________________ /=? ft P* 4 ** ft ft 4 ft 4- ft A S32 3 a C3SV 6?SV <6360 7Oy n 6 ?c/2 6S 6 c tv/? CN 2 6053 QVJ GVCS 6 WC, C9ZH 7 0ZI Q i- S/0 6 6 63 c csz 0 _fP?_ o Is ft ft ft ft 4 ftjr ft ft A 6S2Z Sj 67*7 7 36S 6SZ-6 7'n o *V 7/33 7*f0 > coS 7 \fi Ml B 6 ?7S 0 6? to 730Z 6 13JS 7 S?Z 725 6- 7 6 07 7 37 Z V? ' - C.^us/y srSSt/gr 77^ - / _________________________ B- ~ ' /7>CS. (/J <SS /?(/ST CS/eT //S Cfc/s/f__ 7J?. /'///i /? -____>/os /ry /P/zt/g <? pr/ss/T-y_______________________ ______ FIGURE _I CTD001325 -Page 11- DISCUSSION: 1). There was an increase in crush modulus due to "double autoclaving" at the plant of about 10.1 percent, and at the shop of about 7.8 percent for an average of 9.0 In arriving at this figure, an average difference of 108 pounds per square inch between the control samples from Pipe I (6665) and those from Pipe 2 (6773) was applied in the calculation. Further, it should be noted that a significant strength difference due to position existed in both pipe (see Figure I), thus tending to overshadow the results. 2). Another consideration is the density difference between Pipe 1 and Pipe 2 ) 0'0630 to 0.0646 for the plant samples, and 0.0627 to 0.0640 for the shop ' samples). Since strength is roughly proportional to the density squared, this could account for about 5.1 percent of the plant increase, and about 4.2 percent of the shop increase for an average of 4.7 out of the 9.0 pre viously calculated for "double autoclaving". 3). It should also be noted that the difference in crush modulus for the shop samples averaged about 2.6 percent higher than that for the plant samples. 4). Based on the foregoing considerations, the increase in crush strength due to "double autoclaving" alone averages about 4.3 percent. Further, the results obtained with the plant and the shop autoclaves are approximately equivalent. 5). As indicated in Table III, the increase in strength resulting from "double autoclaving" is accompanied by the expected increase in tobermorite content and decrease in unreacted silica. CTD001326 -Page 12RECOMMENDATIONS: It is considered that the effect of "doable autoclaving" should be studied in more detail in the laboratory under various precure, autoclaving, and wetting conditions, using cements and silicas from the various asbestos-cement pipe plants. A recommend ation to this effect has been included in the proposed study entitled Asbestos-Cement Curing Investigation (Project 345). CTD001327